S
M
T
W
T
F
S
31
86°
53°
1
90°
52°
2
90°
53°
3
92°
55°
4
69°
53°
5
75°
45°
6
82°
45°
7
87°
54°
8
84°
53°
9
81°
50°
10
79°
53°
11
74°
55°
12
78°
49°
13
77°
47°
14
79°
47°
15
69°
47°
16
71°
52°
17
74°
45°
18
78°
45°
19
77°
47°
20
86°
47°
21
80°
47°
22
67°
46°
23
73°
36°
24
83°
43°
25
84°
44°
26
73°
54°
27
77°
40°
28
79°
44°
29
83°
46°
30
72°
51°
1
74°
49°
2
71°
45°
3
65°
49°
4
60°
41°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Boulder
Boulder's September 2025 forecast shows daily high temperatures ranging from ° to °, with overnight lows between ° and °. The average high for September is ° with an average low of °. AccuWeather's monthly forecast extends further ahead than any other source, with day-by-day RealFeel® Temperatures giving a complete picture of how September weather will actually feel in Boulder. See also: October | November | December.
